Molecular weight regulation in polymerization of vinylidene monomers using eugenol as regulator



United States Patent MULECULAR WEIGHT REGULATIGN IN Pfililly- ERKZATEUN 0i? VIWYLEENE MQNQMERS USZNQ EEJGENGL AS REGULATQR Richard E. Delacretaz and Robert L. Walter, Springfield, Mass, assignors to Monsanto Company, a corporation Delaware No Drawing. Filed Nov. 3, 1961, Ser. No. 149,875 4 Claims. (Cl. 26085.5)

This invention relates to the polymerization of a free radical-polymerizable material including a polar monomer and more particularly relates to a method of regulating the molecular weights of polymers prepared by polymerizing such a free radical-polymerizable material in the absence of an organic diluent.

The tendency of certain tree radical-polymerizable materials to polymerize to very high molecular weight polymers under normal polymerization conditions is already well known. These very high molecular weight polymers have the disadvantage of being diiiicultly processable, i.e., unable to be processed without the use of special processing equipment except at temperatures so high as to have a detrimental effect on the strength and color of the processed polymers.

Various techniques have been proposed for regulating the molecular weights of such polymers so as to make them more easily processable. One of these techniques is to conduct the polymerization in an organic diluent. This technique is effective as a means of lowering molecular weight, but it has the disadvantages of increased cost and inconvenience of separating the polymer from the organic diluent. Other proposed techniques avoid the disadvantages of solvent polymerization but have unfortunate isadvantages of their own, e.g., raising the polymerization temperature increases the danger of a runway polymerization, and using a mercaptan as a chain transfer agent contributes a very unpleasant odor to the polymers.

An object of the invention is to provide more easily processed polymers of the type prepared by polymerizing a free radical-polymerizable material including a polar monomer.

Another object is to provide a novel process for regulating the molecular Weights of such polymers without employing an organic diluent in the polymerization reaction mixture.

These and other objects are attained by conducting the polymerization of a free radical-polymerizable material including a polar monomer, as hereinafter more completely described, in the absence of an organic diluent and in the presence of 0.2-5% of eugenol, based on the weight of the free radicaLpolymerizaole material.

The following examples are given to illustrate the invention. Unless otherwise specified, quantities are mentioned on a weight basis, and polymer properties are determined under the same conditions in each part of any one example.

EXAMPLE I Polyvinyl Chloride PART A Charge 100 parts of purified vinyl chloride monomer, 150 parts of water, 0.15 part of lauroyl peroxide, and 0.5 part of a water-soluble acrylic acid-Z-ethylhexyl acrylate (-90:10) copolymer to a suitable reaction vessel. Seal the vessel and tumble it in a constant temperature bath at 50 C. for 15 hours. The polymeric product has a specific viscosity of 0.540, measured as a solution of 0.25% of the polymer in cyclohexanone.

PART B Repeat Part A except for including 1 part of eugenol in weight of the free radical-polymerizable material.

3,160,619, Patented Dec. 8, 1964 in the charge to the reaction vessel. The polymeric product has a specific viscosity of 0.365.

EXAMPLE II Styrene-Acrylonilrile Copolymer PART A Charge 70 parts of styrene, 30 parts of acrylonitrile, parts of water, 0.5 part of di t-hutyl peroxide, and 0.03 part of a water-soluble acrylic acid-Z-ethylhexyl acrylate (90:10) copolymer to a suitable reaction vessel. Heat with agitation at C. for 4 hours and then at C. for 4 hours. Strip the bead slurry of unreacted monomers, Wash, and dry. The polymeric product has a specific viscosity of 0.200 (measured as a solution of 0.1% or" the polymer in dimethylformamide).

PART B Repeat Part A except for including 1 part of eugenol in the charge to the reaction vessel. The polymeric product has a specific viscosity of 0.135.

The invention is a method of regulating the molecular weights of polymers prepared from a free radical-polymerizahle material including a polar monomer without employing an organic diluent. The molecular weight regulation is achieved by conducting the polymerization of the free radical-polymerizable material in the presence of a minor amount of eugenol.

The amount of molecular weight regulator employed in the practice of the invention is in the range of 0.25%, usually (LS-3%, based on the weight of the free radicalpolymerizahle material. Eugenol is ineffective as a molecular weight regulator at concentrations lower than 0.2%. Concentrations higher than 5% are usually undesirable, either because the higher concentration causes too great a reduction of the molecular Weight of the polymer or because the amount of molecular weight regulator which becomes chemically-combined into the polymer is large enough to noticeably afiect polymer properties other than the properties attributable to molecular weight. A particular advantage of the molecular weight regulator of the in ention is its ability to act as a molecular weight regulator at such low concentrations that substantially its only contribution to the properties of the polymers prepared in its presence is an improvement in processability.

The free radical-polymerizable materials which are polymerized in the presence of the molecular weight regulator of the invention are materials including a polar monomer, i.e., a monomer which has a dipole moment of at least 1.0 Debye unit. Particularly suitable materials are: 7

(1) Polar vinylidene monomers, such as acrylonitrile, methacrylonitrile, vinyl chloride, an alkyl acrylate (e.g., methyl acrylate, ethyl acrylate, butyl acrylate, Z-ethylhexyl acrylate, dodecyl acryiate, etc.), an alkyl methacrylate (e.g., methyl methacryiate, butyl methacrylate, etc.), and mixtures thereof,

(2) Mixtures of such polar vinylidene monomers with copolymerizable monomers, such as dialkyl m-aleates, dialkyl fumarates, acrylic acid, methacrylic acid, conjugated dienes (e.g., butadiene), monovinylidene aromatic hydrocarbons (e.g., styrene, alpha-methylstyrene, alphaethyl-styrene, 0-, m-, and p-methylstyrenes, o-, m-, and p-methyl-alpha-methylstyrenes, p-isopropylstyrene, ar-dibutylstyrenes, vinyl napththalene, etc), and g (3) Mixtures of non-polar vinylidene monomers with one or more copolymeriza'ole polar compounds other than the polar monomers mentioned above, such as monoor dialkyl mal-eates or =fumarates, maleic anhyride, acrylic acid, methacrylic acid, etc.

A polar monomer should comprise at least 10% of the cordingtoone of .thepreferredembodiments. of the invention, the free radical-polymerizable material consists of -90% by Weight of one or more monovinylidene aromatichydrocarbons and 9010%'by weight of acrylonitrile and/ or methacrylonitrile.

The polymerization of the free radical-polymerizable material in the presence of the molecular weight regulator of the invention is conducted in the absence of an organic diluent. Polymerization may be accomplished by any of the mass, suspension, or emulsion polymerization tech- .niques conventionally employed for the polymerization of such materials, usually at temperatures in the range of 30200 C. at atmospheric or superatmospheric pressure. The reaction mixture should contain a free radical polymerizationinitiator, such as a peroxy or azo Compound, and any ingredient required by the particular polymerization technique employed, e.g., Water, an emulsifying agent, a suspending agent, etc. Optional ingredients, such as antioxidants, plasticizers, etc., can also be included in the reaction mixture if desired.

A preferred embodiment of the invention is the use of the molecular weight regulator in polymerization reactions which are conducted in an aqueous medium. I rdinarily in such reactions the weight ratio of water to'free radical-polymerizable material is in the range of '9:1 to 2:3. The emulsifying agent, when employed, can

'be of the anionic, cationic, or non-ionic type; the suspending agent, when employed, can be inorganic or organic.

'It is within the scope of the invention to conduct the polymerization in the presence of a preformed polymer, e.g., polybutadiene, a rubbery 'butadiene-styrene copolymer, or the like, to graft polymeric chains of the free radical-polymerizable material onto the preformed polymer backbone. The molecular weight regulator serves to shorten the chains grafted onto the polymer backbone as well as to lower the molecular weight of any co-formed, ungraftedpolymer of the free radical-polymerizable material.

The. products of the invention are polymers which contain a minor amount of chemically-combined molecular Weight regulator and have lower molecular weights than the corresponding polymers prepared in the absence of the molecular weight regulators. Because of their lower molecular weights, they are more easily processable and can be processed, e.g., extruded, molded, etc., in conventional processing equipment without requiring the use of extreme temperatures which .would have a detrimentalefiect on the strength and color of the products.

The invention is particularly advantageous in that it accomplishes molecular weight regulation without the aid of organic diluents, malodorous mercaptans, or reactive materials which would have to be used in such large amounts as to have a noticeable efiect on other polymer properties as well as on processability.

It is obvious that many variations can be made in the products and processes set forth above without departing from the spirit and scope of this invention.

What is claimed is:

1. In a process for polymerizing a free radical-polymerizable material of the group consisting of (a) a polar vinylidene monomer of the group consisting of acrylonitrile, methacrylonitrile, vinyl chloride, an alkyl acrylate, an alkyl methacrylate, and mixtures thereof, ([7) mixtures of said polar vinylidene monomer with a copolymerizable monomer of the group consisting of a dialkyl maleate,

.a dialkyl fumarate, acrylic acid, methacrylic acid, a convjugatecl diene, a'monovinylidene aromatic hydrocarbon, and mixtures-thereof, and '(c) mixtures of a non-polar vinylidene monomer with a copolymerizable polar monomer of the group consisting of a monoalkyl maleate, a monoalkyl fumarate, a dialkyl maleate, a dialkyl fumarate,

maleic anhydride, acrylic acid, methacrylic acid, and

mixtures thereof in the presence of a free radical polymerization initiator, the improvement which comprises conducting the polymerization in the presence of 0.2-5 of eugenol, based on the weight of the free radical-polymerizable material.

2. A process as in claim 1 wherein the free radicalpolyrnerizable material consists of l090% by weight of a monovinylidene aromatic hydrocarbon and -10% by weight of acrylonitrile.

3. A process as in claim 2 wherein thefree radicalpolymerizable material consists of 10-90% by weight of styrene and 90-10% by weight of acrylonitrile.

4. A process as in claim 1 wherein the polymerization is conducted in an aqueous medium.

References Cited in the file of this'patent UNITED STATES PATENTS 2,129,478 Rohm Sept. 6, 1938 ;2,556,488 Wakeford et a1 June 12, 1951 3,110,702 Delacretaz Nov. 12, 1963 

1. IN A PROCESS FOR POLYMERIZING A FREE RADICAL-POLYMERIZABLE MATERIAL OF THE AGROUP CONSISTING OF (A) A POLAR VINYLIDENE MONOMER OF THE GROUP CONSISTING OF ACRYLONITRILE, METHACRYLONITRILE, VINYL CHLORIDE, AN ALKYL ACRYLATE, AN ALKYL METHACRYLATE, AND MIXTURES THEREOF, (B) MIXTURES OF SAID POLAR VINYLIDENE MONOMER WITH A COPOLYMERIZABLE MONOMER OF THE GROUP CONSISTING OF A DIALKYL MALEATE, A DIALKYL FUMARATE, ACRYLIC ACID, METHACRYLIC ACID, A CONJUGATED DIENE, A MONOVINYLIDENE AROMATIC HYDROCARBON, AND MIXTURES THEREOF, AND (C) MIXTURES OF A NON-POLAR VINYLIDENE MONOMER WITH A COPOLYMERIZABLE POLAR MONOMER OF THE GROUP CONSISTING OF A MONOALKYL MALEATE, A MONOALKYL FUMARATE, A DIALKYL MALEATE, A DIALKYL FUMARATE, MALEIC ANHYDRIDE, ACRYLIC ACID, METHACRYLIC ACID, AND MIXTURES THEREOF IN THE PRESENCE OF A FREE RADICAL POLYMERIZATION INITIATOR, THE IMPROVEMENT WHICH COMPRISES CONDUCTING THE POLYMERIZATION IN THE PRESENCE OF 0.2-5% OF EUGENOL, BASED ON THE WEIGHT OF THE FREE RADICAL-POLYMERIZABLE MATERIAL. 